Known grille shutter apparatuses configured to control an amount of air that flows into a vehicle body from a grille opening portion by opening and closing movable fins provided at the grille opening portion arranged at a frontal portion of a vehicle body are disclosed, for example, in JPS58-139519U, hereinafter referred to as Reference 1, and JP2007-1503A, hereinafter referred to as Reference 2.
A grille shutter apparatus improves an aerodynamic performance, for example, a drag coefficient (Cd), by limiting the amount of air that flows into the vehicle body by closing the movable fins during, for example, driving the vehicle at high speed. At an engine start, the grille shutter apparatus reduces a warm-up time by limiting the amount of air introduced to a radiator by closing the movable fins. In a state where an engine temperature is increasing, the grille shutter apparatus appropriately adjusts the engine temperature by increasing the amount of air flowing into the engine room by opening the movable fins.
Many of the movable fins provided for a grille shutter apparatus includes rotary shafts being rotationally supported. The movable fins are opened and closed based on rotational movements of the rotary shafts.
Air that flows into the vehicle body through the grille opening portion contains water droplets of, for example, rains and fogs. Accordingly, the water droplets adhered to the movable fins may flow along the rotary shafts and enter bearing portions of the grille shutter apparatus. In order for the movable fins to smoothly operate, a predetermined amount of clearance, or space, is provided between each end of a fin portion of the movable fins and the corresponding bearing portion. In a state where the clearances receive air, the air which in turn hits the bearing portions, the water droplets contained in the air may enter bearing portions. The water droplets may contain foreign objects, for example, dusts, or may turn into ice in the bearing portions, each of which may interfere with a smooth rotation of the rotary shafts at the bearing portions. The known grille shutter apparatuses including the grille shutter apparatuses described in Reference 1 and in Reference 2 leave room for improvement in such respect.
A need thus exists for a grille shutter apparatus, which is not susceptible to the drawback mentioned above.